National Gas has released its Gas Winter Review for 2025/26, confirming that Great Britain’s gas system operated safely and reliably through the season despite increasingly changeable operating conditions.

While National Gas does not purchase Britain’s gas, it serves as the Gas System Operator and provides demand and supply forecasts to guide the market.

Across the winter, the network moved around 500TWh of energy, supporting millions of homes and businesses. Overall demand edged down, but the system faced sharper and more frequent shifts in usage, driven by swings in gas-fired power generation and higher heating needs during colder spells.

Although the winter was milder on average, brief periods of severe cold pushed peak demand above the previous year, intensifying pressure at times of highest need.

During these conditions, the analysis indicates gas was pivotal in maintaining electricity system security as renewable output varied.

On 5 January, the coldest day of the winter, gas-fired generation surged from about 2.3GW the day before to 26.1GW. This 23.8GW change formed part of the largest swing in gas-fired output ever recorded over a 36-hour period, underscoring the transmission network’s role in providing fast, flexible capacity and keeping the system stable under stress.

With renewable generation set to continue growing, such rapid shifts in demand are expected to become more frequent, reinforcing the case for a highly responsive gas network to underpin resilience and support a clean, low-carbon power system at short notice.

Key demand and supply trends:

- Great Britain’s gas demand fell by around 4%, and total NTS demand (including exports) by about 2%, mainly due to milder weather and stronger renewable output.

- Demand became much more volatile, with peak daily demand reaching 407 mcm/d — higher than the previous winter despite lower overall usage.

- Gas-fired power output ranged from roughly 2GW to 26GW on consecutive days; the 23.8GW shift over 36 hours was the largest on record and close to the gas fleet’s record output.

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- Non-daily metered demand (primarily heating in homes and smaller businesses) remained the largest share, accounting for nearly 70% of GB demand.

- UK Continental Shelf production declined by around 3%, continuing its long-term downward trend.

- LNG imports rose by 15%, signalling greater reliance on flexible supplies. The United States provided roughly 80%, with the rest sourced from a range of other exporters.

- Storage sites were over 70% full ahead of January’s highest-demand day.

- Flexible sources — including LNG, storage and continental imports — performed as expected, increasing output during high-demand periods.

Glenn Bryn-Jacobsen, Director of Energy Systems and Resilience at National Gas, said:

"Our analysis reaffirms both the ongoing resilience and reliability of the gas network in safeguarding Britain’s energy security in the present and the extent to which it is undergoing a profound structural transition. Operating conditions are becoming increasingly dynamic, with the system no longer characterised by steady demand patterns but by sharp swings driven by weather and renewable output.

"We observed gas-fired power generation ramp up from very low levels to close to record output in the across two consecutive days, and these kinds of swings are becoming more common.

"Gas is therefore playing an increasingly critical role in maintaining energy security within a more renewable-led system, both in providing flexible, responsive capacity at times of low renewable output and in meeting the day-to-day heating needs of millions of homes and businesses across Britain. While this demonstrates the strength of the current system, it also underscores the increasing complexity of operating and balancing the network."

Ian Radley, Chief Commercial Officer at National Gas, said:

"This winter reinforces the growing importance of flexibility and responsiveness across the energy system, particularly as renewable generation becomes a larger proportion of the supply mix. The ability to respond dynamically to unforeseen changes in supply and demand is now a defining feature of system resilience.

"At the same time, the supply picture continues to evolve. Domestic production from the UK Continental Shelf continues to decline, while reliance on flexible sources such as LNG, storage and imports increases.

"Taken together, these trends continue to highlight longer-term structural challenges across the energy system and reinforce the need for coordinated action across government, regulators and industry to safeguard Britain’s future energy security."

"We remain committed to working with Government, Ofgem and across the sector to ensure the network delivers the reliability and flexibility Britain needs, now and in the future."

The National Energy System Operator (NESO) also published its Winter Review and Early Winter View today, indicating the electricity system is expected to remain secure with a sufficient margin to meet demand in line with the government’s reliability standard, broadly consistent with recent winters.

Today’s findings build on National Gas’s Winter Outlook published in October 2025, which pointed to tightening future supply margins as UK Continental Shelf output declines and reliance on global imports grows. They are supported by NESO’s Gas Supply Security Assessment (November 2025), which identified the need for mitigations to protect future resilience.

In February 2026, National Gas published its response to the Government’s Gas System in Transition: Security of Supply consultation, setting out policy options to bolster long-term energy security.

Amid concerns about potential impacts from the conflict in the Middle East, National Gas’s Gas Summer Outlook 2026 indicates the market currently has sufficient capacity to meet near-term demand, and the company continues to report no immediate operational concerns.

National Gas will keep developments under review and provide further analysis in its Gas Winter Outlook later this year. The full report and a one-page summary are available on the National Gas website.